/Engine/Source/Runtime/SlateCore/Public/Widgets/DeclarativeSyntaxSupport.h
SAssignNew
template<class ExposeAsWidgetType> [TSlateDecl](API\Runtime\SlateCore\Widgets\TSlateDecl) && Expose ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< ExposeAsWidgetType > & OutVarToInit )